Load-measuring devices

ABSTRACT

A force-unloading device having a pressure chamber with a flexible wall connected with a movement-unloading means and presenting an inlet for pressure medium. Adjacent the circumference of the inside of the chamber there is provided a guide surface with which the edge portion of the flexible wall engages when placed under load.

United States Patent 2,953,166 9/1960 Carlson g u u uu Inventor Erik Edvard Andersson Alphyddevagen 35, 131 00 Nacka, Sweden Appl. No. 871,838 Filed Oct. 28, 1969 Patented Dec. 14, 1971 Priority Oct. 30, 1968 Sweden 14689/68 LOAD-MEASURING DEVICES 5 Claims, 20 Drawing Figs.

U.S. Cl 92/98 R,

92/103, 73/141 R 1nt.Cl G0ll5/l2 Field ofseereh 73/141, 406;92/99, 100, 101, 103,98; 251/331, 61

References Cited UNITED STATES PATENTS Moller 92/100 Doetsch 92/94 Bauer 25 1/61 Lumpp.... 251/331 Baker 92/104 Trubert 92/104 Hastings 137/788 Primary Examiner-Richard C. Queisser Assistant Examiner-John Whalen Attorney-Cushman, Darby & Cushman flexible wall engages when placed under load.

Patented Dec. 14, 1971 4 Sheets-Sheet 1 INVEN'I'OR. E /k vard A ndenswq MMMT Q s Gdw Affornep Patented Dec. 14, 1971 3,626,814

4 Sheets-Sheet 2 FIGA INVEN'I'OR. 7G Erik dvard nczbrsson Patented Dec. 14, 1971 3,626,814

4 Sheets-Sheet 5 I N V EN TOR. EF/ k Edvard Amok/550m M man w nq flffomeys Patented Dec. 14, 1971 4 Sheets-Sheet 4 FIGJB w m M Q m w m F E 6 7 -3 ,2 I y W Go H BY 045A ash/mm LOAD-MEASURING DEVICES The present invention-relates to a device for unloading force from a pressure chamber having one flexible wall connected witha movement-unloading means and having an inlet for pressure medium at least on one side of the wall. The use of such arrangements or load-measuring devices for difi'erent purposes is steadily increasing. It has been discovered, however, that the flexible wall is liable to failure as a result of the fatigue stresses occuring when the device is in use, which in many cases may cause serious breakdowns in operation and production, for example when the device forms part of a complicated operating or control system.

Accordingly, one object of the present invention is to provide a simple device which circumvents the aforementioned disadvantage and extends the operational life of the flexible wall of the load-measuring device defined in the foregoing.

The device of the invention is mainly characterized in that there is provided adjacent the circumference of the inside of the chamber a guide surface with which the edge portion of the flexible wall engages when subjected to pressure and which is formed as the section surface between a ring-shaped, for example, circular, elliptical, or rectangular, closed cylindrical hollow body, the corners of which are rounded to a greater or lesser extent, 'and a single-curve surface, the generatrices of which are perpendicular to the generatrices of the wall of the hollow body.

By using a guide surface of this construction, the edge of the flexible wall will essentially only be deformed along one main bending axis, whereby all points on a line through the center point of the diaphragm parallel with said main bending axis will undergo maximum bending when pressure fluid is applied, while the two opposing attachment points of the diaphragm, whose connecting lines extend perpendicularly to the main bending axis, are not subjected to bending, but remain in position when pressure fluid is applied to the diaphragm.

A further advantage afforded by the device of the invention over the conventional attachment of the flexible wall, is that the wall functions to a considerable extent as a return means, thereby obviating the necessity of embodying special return springs in the device.

For the purpose of further reducing the stresses and strains on the diaphragm, it is preferred that the guide surface extends in an undulating manner from the two highest opposing points to the two lowest opposing points.

In accordance with one embodiment of the invention particularly suited for practical use, the flexible wall comprises a sealing diaphragm made of rubber, for example, or some other flexible material, and a diaphragm made of metal, for example, such as spring steel and supporting the first-mentioned diaphragm, the rubber diaphragm being provided at those positions most liable to deformation when subjected to pressure, that is the positions opposite the lowest points on the guide surface, with outwardly bulging portions of such form that the rubber material need not be stretched, at least to any appreciable extent, when the diaphragm is deformed by the actuation of the pressure medium.

The constructional expedient of the present invention provides complete sealing of a portion of the flexible wall connected to the movement-unloading means and performing the actual work done, simultaneously as the portion of the flexible wall which provides the aforementioned sealing is not subjected to fatigue creating stresses, since this portion of the flexible wall is provided with means compensatory thereto.

A number of embodiments of the invention will now be described with reference to the accompanying drawings, in which FIG. I is a plan view of a load-measuring device provided with the arrangement of the invention,

FIGS. 2 and 3 are cross-sectional views taken respectively through the lines A-A and 8-8 in FIG. I subsequent to the supply of pressure medium to the load-measuring device,

FIGS. 4 and 5 are corresponding sectional views of the device of FIG. 1 in an unloaded condition,

FIG. 6 is a plan view of a preferred construction of a sealing diaphragm,

FIGS. 7 and 8 are respectively perspective and vertical sectional views, illustrating the diaphragm of FIG. 6 in a stretched condition subsequent to the application of pressure medium,

FIGS. 9 and 10 are respectively part sectional views through the lines A-A and B-B in FIG. 5,

FIG. 11 is a sectional view of a portion of a modified embodiment in which a sealing diaphragm of the type illustrated in FIGS. 6-10 is used,

FIGS. 12-19 illustrate the component parts of the embodiment of FIG. 11 in an unassembled condition, and finally FIG. 20 shows in perspective another preferred embodiment of the sealing diaphragm placed on the support diaphragm in an unloaded condition.

In the drawings there is shown a load-measuring device or pressure cell 1, which comprises an upper cover member 2 and a lower cover member 3, defining a pressure chamber in which is arranged a diaphragm 4 made of metal, for example, such as spring steel. The center portion of the diaphragm is connected to a force-unloading means in the form of a piston rod 5. Pressure medium, for example air under pressure, is passed to the load-measuring device, via an opening 6.

Located on the under surface of the diaphragm 4 is a diaphragm guide surface 7a, with which the edge portion of the diaphragm engages when subjected to pressure and which has the shape of a curved geometric surface, produced by a straight line which moves parallel with its own extension. The guide surface comprises the edge surface 70 on a ring 7, although it may be formed by a shoulder at the circumference of the pressure chamber 10, defined by the cover members 2 and 3.

As a result of the particular configuration of the guide surface, the edge of the diaphragm 4 will be deformed most at two opposed positions, which in the embodiment of the device shown in FIG. 2, fall in a plane normal to the plane of the paper through the symmetry axis of the device. In the section shown in FIG. 3, these positions are located in the plane of the paper at the periphery of the device, on opposite sides of the piston 5.

The opposing diaphragm attachment positions shown in FIG. 2 and falling in the plane of the paper are not deformed, however, since the highest points of the support ring 7 are situated at these positions.

Arranged on the side of the diaphragm 4 confronting the pressure chamber I0 is a sealing diaphragm 8, made of rubber or some other flexible material. The rubber diaphragm presents around its circumference a lip or bead 8a, which is secured between a clamping surface, which extends peripherally beyond the guide surface 70 and which comprises, for example, the edge surface of a clamping or filling ring 11, and a portion of the wall of the chamber 10. In the exemplary embodiment of FIG. 2, the upper cover member 2 may therefore be provided with a peripheral, outwardly bulging member which engages the lip 80.

When pressure medium is supplied to the pressure chamber 10, the peripheral edge portion of the diaphragm 4 will follow .the arcuate guide surface 7a, whereupon the diaphragm is flexed or bent in only one main bending direction and consequently is not subjected to such bending loads as would rapidly result in fatigue and fracture of the diaphragm. At the same time the arrangement provides for the necessary sealing of the rubber diaphragm 8, which is supported across a large portion of its area by the diaphragm 4, thereby substantially eliminating the risk of the diaphragm 8 rupturing when the device is in use. Nevertheless, when pressure fluid is introduced into the pressure chamber, a considerable part of the peripheral portion of the rubber diaphragm 8, at the positions where the lowest points of the guide surface 7a are situated, will be urged against the wall of the pressure chamber I0.

The modified embodiments of the sealing rubber diaphragm 8 illustrated in FIGS. 6-10 further reduce the risk of fatigue on said diaphragm. In accordance with this embodiment, the rubber diaphragm 8 is provided at those positions most liable to deformation as a result of the pressure applied thereon, that is opposite the lowest points on the guide surface, with outwardly bulging portions 8b of such form that the rubber need not be extended to any appreciable extent when the diaphragm is deformed under pressure. As shown in FIG. 6, the bulge portions 8b are essentially half moon shaped when seen in plan.

The embodiment of the load-measuring device illustrated in FIG. 11 embodies a sealing membrane 8 of the type illustrated in FIGS. 6-10. In this embodiment, as also in the preceding embodiments, the metal diaphragm 4 is provided on its undersurface with two support plates 15, 16, and an additional support plate 17 is mounted over the rubber diaphragm 8, which embodies a length-compensating lip or bead 8b. Similar to the embodiments of FIGS. 1-5, there is arranged on the outside of the support ring 7, presenting the guide surface 7a, a filling ring 11. FIGS. 12-19 illustrate the component parts of the load-measuring device in an unassembled condition.

FIG. 20 illustrates another preferred embodiment of the sealing member 8 placed on the support diaphragm 4 and the hollow body 7, which presents the guide surface 70 and is located beneath said diaphragm 4, all in an unloaded condition. The diaphragm 8', which may also be made of rubber for example, is in this case provided with bulging portions 8b which are of different configuration to those provided on the diaphragm of FIG. 6 and which are positioned opposite the lowest points of the guide surface 7a. Since these edge portions of the sealing diaphragm 8, which are raised in the axial direction of the load-measuring device, when no load is placed thereon, that is when the whole of the periphery of the supporting diaphragm 4 bears against the guide surface 7a, substantially fill up the downwardly arcuate portions of the guide surface, it is not necessary to extend the diaphragm 8 to any appreciable extent when the diaphragm is deformed as a result of the load placed thereon.

What l claim is:

1. In a device for unloading the force from a pressure chamber having a diaphragm member connected with a movable force-unloading means and presenting an inlet for pressurized fluid at least on one side of the diaphragm member,

the improvement comprising:

an annular abutment surface provided adjacent the circumference of the inside of the chamber with which the edge portion of the diaphragm member engages when placed under load, which surface has the form of the intersection between a hollow body having the shape of said chamber's circumference and a cylindrical surface having an axis which is perpendicular to that of the hollow body, wherein the abutment surface has two opposing elevations and two opposing depressions therein, and the abutment surface extends in the form of an arch from the elevations to the depressions and wherein the diaphragm member comprises a sealing diaphragm made of rubber or other flexible material, and a second diaphragm supporting said sealing diaphragm and being made of metal, such as spring steel, said rubber diaphragm at the positions most liable to deform under load, said positions being opposite the depressions on the abutment surface, is provided with axially outwardly bulging portions of such form that when the diaphragm is deformed under pressure the material of the diaphragm is not required to extend to any appreciable extent.

2. The device of claim 1, wherein the outwardly bulging portions are essentially in the shape of a half moon when seen in plan view.

3. The device of claim l, wherein the bulging portions, which are positioned opposite the lowest points of the abutment surface, consist of arcuate portions raised in the axial direction of the load-measuring device.

4. The device of claim I, wherein the sealing diaphragm is provided around the periphery thereof with a lip secured between a clamping surface, which may be the edge of a clamping ring and extends peripherally beyond the abutment surface, and a portion of the wall of the chamber, while the support diaphragm rests freely on the abutment surface.

5. The device of claim 1, wherein the support diaphragm,

being made of metal, such as spring steel is embodied in the diap ragm member and serves as the diaphragm return means, thereby obviating the need of special return springs or like member. 

1. In a device for unloading the force from a pressure chamber having a diaphragm member connected with a movable forceunloading means and presenting an inlet for pressurized fluid at least on one side of the diaphragm member, the improvement comprising: an annular abutment surface provided adjacent the circumference of the inside of the chamber with which the edge portion of the diaphragm member engages when placed under load, which surface has the form of the intersection between a hollow body having the shape of said chamber''s circumference and a cylindrical surface having an axis which is perpendicular to that of the hollow body, wherein the abutment surface has two opposing elevations and two opposing depressions therein, and the abutment surface extends in the form of an arch from the elevations to the depressions and wherein the diaphragm member comprises a sealing diaphragm made of rubber or other flexible material, and a second diaphragm supporting said sealing diaphragm and being made of metal, such as spring steel, said rubber diaphragm at the positions most liable to deform under load, said positions being opposite the depressions on the abutment surface, is provided with axially outwardly bulging portions of such form that when the diaphragm is deformed under pressure the material of the diaphragm is not required to extend to any appreciable extent.
 2. The device of claim 1, wherein the outwardly bulging portions are essentially in the shape of a half moon when seen in plan view.
 3. The device of claim 1, wherein the bulging portions, which are positioned opposite the lowest points of the abutment surface, consist of arcuate portions raised in the axial direction of the load-measuring device.
 4. The device of claim 1, wherein the sealing diaphragm is provided around the periphery thereof with a lip secured between a clamping surface, which may be the edge of a clamping ring and extends peripherally beyond the abutment surface, and a portion of the wall of the chamber, while the support diaphragm rests freely on the abutment surface.
 5. The device of claim 1, wherein the support diaphragm, being made of metal, such as spring steel is embodied in the diaphragm member and serves as the diaphragm return means, thereby obviating the need of special return springs or like member. 